Opposite Leg Research Articles

Hemodynamic Stability after Pediatric Epidurals

We would like to thank Dr. Rebecca Lowery for her interest in our case report. The quote to which Dr. Lowery referred was only half of our original sentence, which read “The absence of epidural spread was assessed by hemodynamic stability after the performance of the blocks and by the presence of an adequate reaction to pin prick of the opposite leg after emergence.” Although we also recognize that the hemodynamic changes associated with neuroaxial blockade may be absent or less pronounced in infants and young children, it is critical to acknowledge also the following. (1) Dohi et al. 1and Oberlander et al. 2reported on a very limited number of infants and young children. Although Dohi et al. 1reported that significant hypotension might be observed in young children around 5 yr of age and older, extrapolating from these articles, the concept that 5 yr represents the absolute lower limit for children to be exposed to such risk following a neuroaxial block may be excessive. (2) More importantly, in infants and young children, any diagnosis is often the result of the convergence of symptoms, and therefore, even if the risk is minimum, it should not be ignored. (3) We would like to believe that Dr. Lowery is not recommending not monitoring blood pressure following the performance of lumbar plexus block in infants and young children. In conclusion, we are happy to have provided an opportunity for Dr. Lowery to remind us about the expected hemodynamic changes associated with neuroaxial blocks in infants and young children. However, we would like to maintain that monitoring blood pressure is essential when performing a lumbar plexus block, even in this patient population.

Instrumental learning within the spinal cord: II. Evidence for central mediation

Rats spinally transected at the second thoracic vertebra can learn to maintain their leg in a flexed position if they receive legshock for extending the limb. These rats display an increase in the duration of a flexion response that minimizes net shock exposure. The current set of experiments was designed to determine whether the acquisition of this behavioral response is mediated by the neurons of the spinal cord (i.e., is centrally mediated) or reflects a peripheral modification (e.g., a change in muscle tension). Experiment 1 found that preventing information from reaching the spinal cord by severing the sciatic nerve blocked the acquisition of this behavioral response. Spinalized rats also failed to learn if the spinal cord was anesthetized with lidocaine during exposure to response-contingent shock (Experiment 2). Experiment 3 demonstrated that prior exposure to response-contingent shock on one hindleg facilitated acquisition of the response when subjects were later tested on the opposite leg. These findings suggest that acquisition of the instrumental response depends on neurons within the spinal cord.

Expression of aromatase in the human growth plate.

Aromatase catalyzes the synthesis of estrogen from its androgen precursors. Estrogen is known to be important in regulating long bone growth and epiphyseal plate closure. To assess whether there may be growth plate-specific production of estrogen, we performed reverse transcriptase polymerase chain reaction (RT-PCR) to determine whether aromatase transcripts are present in the human growth plate. Immunohistochemistry was also employed to identify the specific sites of expression. Growth plates were obtained from an adolescent male and female undergoing ephysectomy to counter premature growth plate closure in the opposite leg. Aromatase transcripts were detected in RNA preparations from both growth plates. The aromatase protein was mainly expressed in the zone of maturation and the hypertrophic zone, with greatest expression in the latter. Since estrogen receptors are known to be expressed in chondrocytes, this data is consistent with a role for local estrogen production in the autocrine/paracrine control of long bone growth and growth plate maturation.

Extent of Ischemia in Skeletal Muscle Compared during Circulatory Occlusion and Exsanguination

Extent of Ischemia in Skeletal Muscle Compared during Circulatory Occlusion and Exsanguination Korth et al.(page 1407) In 18 patients scheduled to undergo elective surgery of the lower limb, Korth et al. obtained permission to insert microdialysis probes into both quadriceps femoris muscles to quantify the extent of ischemia produced by use of a tourniquet. The probes on the side of surgery were placed midline 2 cm below the tourniquet, and the probes on the opposite leg served as controls. The probes were perfused at a rate of 2 μl/min with sterile Ringer’s solution. Samples were collected on ice at 15-min intervals and stored for later analysis. Blood samples were obtained from the femoral vein before ischemia and at 2, 60, and 120 min after deflation of the tourniquet.The patients were assigned to one of two groups. One group underwent surgery under circulatory occlusion, with the leg elevated for a few minutes followed by tourniquet inflation to a pressure of 380 mmHg to surpass arterial blood pressure. In the second group, the leg was elevated and exsanguination was accomplished with use of an elastic Esmarch bandage wrapped around the ankle and rolled toward the body, followed by tourniquet inflation to 380 mmHg and removal of the bandage.At a flow rate of 2 μl/min, average baseline concentrations in the dialysate were 2.5 mm for glucose, 1.7 mm for lactate, 5.2 μm for choline, and 14.3 μm for hypoxanthine. Within 30 min of circulatory occlusion by tourniquet, extracellular glucose concentrations decreased 40%. At the same time, interstitial levels of lactate and hypoxanthine increased in linear fashion to 206% and 241% of baseline levels, respectively. These indicators of tissue ischemia change were even more increased after exsanguination—to 268% of baseline for lactate and to 286% of baseline for hypoxanthine. The authors conclude that circulatory occlusion is less demanding on muscle tissue than is exsanguination.

Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model

To determine if a commercially available negative-pressure venom extraction device (Extractor) reduces local tissue injury after artificial rattlesnake envenomation in a porcine model. We prospectively studied 10 pigs using a crossover design. After the pigs were anesthetized, 25 mg Crotalus atrox venom was injected obliquely with a 22-gauge needle 7 mm deep into subcutaneous tissues proximal to the ventral hind hoof. Pigs were randomized to receive either the Extractor (applied 3 minutes following envenomation and left in place for 30 minutes) or no Extractor. The protocol was repeated 14 days later by using the alternate treatment group and opposite hind leg for each animal. We measured leg circumference at standardized locations on the hoof, foreleg, and thigh at baseline and then 1, 2, 3, 4, 5, 6, 24, 48, 72, and 96 hours following venom injection. Maximal changes in circumference at 6 hours were compared using the paired t test. Minimum residual swelling at up to 96 hours was similarly compared. Maximal 6-hour swelling was similar with and without the Extractor: the hoof difference with the Extractor was -0.1% (95% CI = -3.4% to 3.2%, P = .95), foreleg difference was 0.3% (95% CI = -4.1% to 4.7%, P = .88), and thigh difference was -2.8% (95% CI = -10.0% to 4.4%, P = .40). Minimum residual swelling at up to 96 hours was also similar with and without the Extractor: hoof difference with the Extractor was 1.2% (95% CI = -5.6% to 8.0%, P = .70), foreleg difference was 0.6% (95% CI = -3.7% to 4.9%, P = .76), and thigh difference was 0.3% (95% CI = -2.4% to 3.0%, P = .81). A circular lesion identical in size and shape to the Extractor suction cup, which later necrosed and resulted in tissue loss, developed where the device had been applied in 2 animals. No such lesions occurred in legs not treated with the Extractor. No benefit was demonstrated from Extractor use for artificial rattlesnake envenomation in our animal study. The skin necrosis noted in 2 Extractor-treated extremities suggests that an injury pattern may be associated with the device.

Large transverse fasciocutaneous leg flap: whole leg flap

Large defects of leg and sole often need massive tissue transfer. As an alternative to microvascular transfer, we have developed a fasciocutaneous flap in which almost the whole of the skin of the opposite leg is transferred based just on the septocutaneous perforators of the posterior tibial artery. The flap has been used as a cross-leg fasciocutaneous flap with potential for use as a free flap by taking a segment of the posterior tibial artery. Our experience with 11 cases is presented. Two patients suffered marginal necrosis while donor site problems were seen in another two patients. We have found this flap to be safe, technically easy and with minimal donor-site morbidity.

Development of Postural Adjustment During Gait Initiation: Kinematic and EMG Analysis

The authors studied the development of postural adjustments associated with the initiation of gait in children by using kinematic and electromyographic (EMG) analysis. Participants (N = 28) included infants with 1-4 and 9-17 months of walking experience, children 4-5 years of age, and adults. Anticipatory postural adjustments (APA) were present in the youngest age groups, including a clear anticipatory lateral tilt of the pelvis and the stance leg, which enabled the child to unload the opposite leg shortly before its swing phase. An anticipatory activation of the hip abductor of the leg in stance phase prior to heel-off was found, suggesting pelvis stabilization. APA did not appear consistently until 4-5 years of age. A decrease in segmental oscillations occurred across the ages, indicating better control of intersegmental coordination in the frontal and sagittal planes during the postural phase of gait initiation. Young walkers presented APA involving movements of both the upper and the lower parts of the body, whereas, like adults, 4- to 5-year-olds were able to laterally shift only the pelvis and the stance leg. The oldest children and the adults also showed lower activation levels of hip and knee muscles but higher activation at the ankle level. Those kinematic and EMG results taken together suggest a clear developmental sequence from an en bloc operation of the body through an articulated operation with maturation, walking experience, or both.

Overexpression of Fas-Ligand by neuroblastoma: A novel mechanism of tumor-cell killing

Background/Purpose: Binding of Fas ligand (Fas-L) to the membrane-bound Fas receptor incites a series of intracellular events that results in programmed cell death or apoptosis. Although this apoptotic phenomenon plays a key role in down-regulating cytotoxic T cells, the authors have shown previously that pancreatic beta cells (bTC) overexpressing Fas-L paradoxically undergo accelerated rejection that is dependent on a Fas/Fas-L interaction. This study evaluates whether a neuroblastoma (NB) cell line manipulated to overexpress Fas-L undergoes similar destruction and whether tumor-specific protective immunity can be produced.Methods: The authors transfected NB cells (SK-N-MC) with either mFas-L cloned into a pcDNA3.1/Zeo plasmid vector (NB/Fas-L) or with the vector alone (NB/control). Successful transfection of Fas-L was characterized by reverse transcription polymerase chain reaction (RTPCR) and the ability of transfectants to induce apoptosis of Fas-sensitive T cells (Jurkat). Expression of Fas and Fas-L in untransfected NB clones was characterized by immunohistochemistry and RNase protection assay (RPA). Apoptosis was measured by FACScan analysis using an Annexin V assay. A total of 3 × 106 NB/control and NB/Fas-L cells were implanted subcutaneously into the hind leg of Balb/C SCID mice. Tumor-specific protective immunity was also tested in this model by inoculating mice with NB/Fas-L before implanting NB/control cells.Results: Zeocin resistance and RT-PCR confirmed successful transfection of Fas-L into NB cells. Fas Ligand transfectants induced apoptosis in 17.6% ± 2.9% of Fas-sensitive T cells, whereas controls induced apoptosis in only 2.8% ± 1.2% (P= .01, n = 3). Although Fas appears to be constitutively expressed by NB in low amounts, introduction of Fas-L into NB cells did not induce suicide or affect tumor cell growth in vitro. In vivo, NB cells expressing Fas-L failed to grow in SCID mice (n = 3), whereas controls grew rapidly in all animals until death (n = 3). NB/control cells implanted into the opposite leg of mice that rejected initial NB/Fas-L transfectants also grew rapidly (n = 3) implying no protective immunity.Conclusions: Overexpression of Fas-L in NB clones targets such cells for rapid destruction even in immune compromised hosts, suggesting potential utility of Fas-L in combating NB. In this SCID mouse model, the observed effect is probably neutrophil mediated and does not provide tumor-specific protective immunity.

Scintigraphic evaluation of tibial shaft fracture healing

A scintigraphic study of the healing process of type A and B closed tibial shaft fractures was carried out in 40 cases treated non-operatively, comprising 32 men and eight women aged 30.6 yr on average. Scintigraphic scans were obtained with technetium methylenediphosphonate (MDP-Tc99m, 25 mCi) at 6, 12 and 24 weeks after the fracture and an activity index was calculated taking the mean of three consecutive uptake counts for both fractured and normal opposite leg, used for comparison. The results showed that the activity index in general decreased progressively from the first to the third evaluation, with little difference in behaviour between the two types of fractures. However, for B type fractures the activity index remained stable from the first to the second evaluation, followed by a marked decrease at the third evaluation, with a comparable end result for both fracture types. It was concluded that a decrease of the activity index occurs in both types of closed fractures undergoing uneventful healing and that such a decrease can be taken as a parameter for further studies which include delayed union and non-union.

Fever, cough, and nodules on ankles

A 26-year-old woman with fever; headache, and a dry cough was admitted in September, 1998, to the Hyogo College of Medicine Hospital with multiple nodules on her chest radiograph. She had no relevant medical history and was in good general health. She had not travelled abroad. Her job was in an electrical appliance shop. Examination on admission showed cervical lymphadenopathy, leucocytosis 16·8×106/L, and eosinophilia (61%). There were no neurological abnormalities and her optic fundae were normal. Chest radiography and computed tomography (CT) showed multiple nodules in both lung fields. The size and location of these shadows changed during her stay in hospital. CT, magnetic resonance imaging (MRI), and ultrasonography of the liver were done. Non-contrast CT showed multiple low-density hepatic nodules. Hepatic-arterial-dominant phase-contrast CT showed several well-defined hepatic nodules. Portal-venous-dominant phase-contrast CT showed homogeneous enhancement of the lesions. MRI findings also suggested an inflammatory process, not a malignant tumour or haemangioma. Histological examination of specimens obtained from liver biopsy and transbronchial lung biopsy showed only extensive eosinophilic infiltration. There were elevated concentrations of immunoglobulin E (IgE, radioimmunosorbent test 8980 U/mL), specific IgE against Ascaris lumbricoides (radioallergosorbent test 74 UA/mL), and specific IgE against Anisakis simplex (radioallergosorbent test 1·81 UA/mL). Ouchterlony's double diffusion test showed a strong precipitin band against the larval excretory-secretory antigen of Toxocara canis. ELISA with the larval excretory-secretory antigen of T canis was positive. There was a small brown itchy nodule on her left ankle on admission. This was thought to be prurigo and was treated unsuccessfully with topical steroids. Similar skin lesions then appeared on the opposite leg.

Outcome measures after lower extremity bypass surgery: there is more than just patency.

Arterial occlusive disease is a generalized, progressive, and disabling condition that can significantly influence the quality of a patient’s life. When it affects peripheral vessels this chronic disease may cause considerable morbidity, particularly when it progresses to gangrene. At other sites it is responsible for an increased mortality from myocardial infarction and stroke. To improve some of this unfavourable outlook lower extremity bypass surgery down to the level of the ankle and foot has been recommended, even in elderly patients with extensive disease. Such procedures, however, are associated with a high failure rate leading to further surgical interventions and hospital stays. The traditionally reported outcomes of bypass operations are graft patency, limb salvage and patient survival 1 , but these indicators of surgical success are limited as measurements of outcome because they do not tell the whole story from the patient’s perspective. All vascular surgeons know that major amputation may sometimes be necessary in spite of graft patency, and that graft occlusion is not always associated with a reduction in quality of life. For a proper appreciation of the situation many factors must be considered, particularly delayed wound healing, residual postoperative pain and leg swelling, episodes of recurrent ischaemia, number of reoperations, maintenance of ambulation and residential status, opposite leg problems and cardiovascular events. Moreover, increasing emphasis has been placed in recent years on assessment of perception of well being, functional capacity and life quality 2 . Nicoloff et al. 3 found that only 14 per cent of patients who had limb salvage surgery achieved the ideal result of an uncomplicated operation with long-term symptom relief, preservation of functional status, and no recurrence or repeat operations. This disappointing picture occurred in spite of an excellent assisted primary graft patency rate of 77 per cent and a limb salvage rate of no less than 87 per cent at 5 years. To allow a more comprehensive view of the effectiveness of bypass surgery, including its impact on daily life and life satisfaction, outcome measurements of vascular interventions must reflect a more complete array of endpoints than those commonly applied. An important issue in the effectiveness of vascular surgery is the need for repeat operative intervention. From recent studies it is evident that many patients who had bypass surgery for limb salvage require ongoing reoperations for persistent or recurrent symptoms until their death, implying significant morbidity, discomfort, and additional costs 3,4 . We believe that additional interventions for a graft-related complication, recurrent leg ischaemia or delayed wound healing should be used as a principal outcome measure in clinical studies. It is also recognized that over time many patients treated for ischaemic symptoms in one leg will return with similar symptoms in the opposite leg 5 . The risk that symptoms will develop in the contralateral limb varies from 8 to 21 per cent per annum and emphasizes that peripheral arterial occlusive disease is essentially a two-limb problem. This information is important for patients, in particular for those with contralateral claudication, and should be discussed in full when considering surgery. Since atherosclerotic disease is

Eccentric muscle action increases site-specific osteogenic response.

Strain magnitude is known to be a primary determinant of the osteogenic response to loading. However, whether bone adaptation to muscle loading is determined primarily by load magnitude is unclear. The purpose of this study was to determine the contribution of load magnitude from muscle action on the site-specific osteogenic response. Twenty young women (12 exercise, 8 control) served as subjects. Bone mineral density (BMD) of the whole body and mid-femur segment and body composition were determined by dual-energy x-ray absorptiometry. Knee extension and flexion strengths were determined on a KinCom dynamometer, with surface electromyography of the vastus lateralis muscle. Exercise subjects trained three times weekly for 18 wk on a KinCom. One leg trained using eccentric knee extension and flexion, and the opposite leg trained using concentric knee extension and flexion. Eccentric exercise demonstrated greater force production with lower integrated electromyographic signal (IEMG) compared with concentric exercise. Significant increases in muscle strength occurred in both exercised legs (P < 0.05), which were of similar relative change. However, only the eccentric trained leg significantly increased mid-femur segment BMD (+3.9%, P < 0.05) and mid-thigh segment lean mass (+5.2%, P < 0.05). These results suggest that eccentric muscle training is more osteogenic than concentric muscle training and that eccentric training is more efficient by attaining higher force production with lower IEMG.

Acute exercise induces GLUT4 translocation in skeletal muscle of normal human subjects and subjects with type 2 diabetes.

Total GLUT4 content in skeletal muscle from individuals with type 2 diabetes is normal; however, recent studies have demonstrated that translocation of GLUT4 to the plasma membrane is decreased in response to insulin stimulation. It is not known whether physical exercise stimulates GLUT4 translocation in skeletal muscle of individuals with type 2 diabetes. Five subjects (two men, three women) with type 2 diabetes and five normal control subjects (5 men), as determined by a standard 75-g oral glucose tolerance test, were recruited to determine whether an acute bout of cycle exercise activates the translocation of GLUT4 to the plasma membrane in skeletal muscle. Each subject had two open biopsies of vastus lateralis muscle; one at rest and one 3-6 weeks later from the opposite leg after 45-60 min of cycle exercise at 60-70% of VO2max. Skeletal muscle plasma membranes were prepared by subcellular fractionation, and GLUT4 content was determined by Western blotting. Plasma membrane GLUT4 increased in each subject in response to exercise. The mean increase in plasma membrane GLUT4 for the subjects with type 2 diabetes was 74 +/-20% above resting values, and for the normal subjects the increase was 71+/-18% above resting values. Although plasma membrane GLUT4 content was approximately 32% lower at rest and after exercise in the muscle of the subjects with type 2 diabetes, the differences were not statistically significant. We conclude that in contrast to the previously reported defect in insulin-stimulated GLUT4 translocation in skeletal muscle of individuals with type 2 diabetes, a single bout of exercise results in the translocation of GLUT4 to the plasma membrane in skeletal muscle of individuals with type 2 diabetes. These data provide the first direct evidence that GLUT4 translocation is an important cellular mechanism through which exercise enhances skeletal muscle glucose uptake in individuals with type 2 diabetes.

Animal model of acute deep vein thrombosis.

To develop an animal model of acute deep vein thrombosis (DVT). In part I of the study nine juvenile domestic pigs were used. Each external iliac vein was transluminally occluded with a balloon catheter. Thrombin was infused through a microcatheter in one leg according to one of the following protocols: (1) intraarterial (IA): 1250 U at 25 U/min in the common femoral artery (n = 3); (2) intravenous (IV): 5000 U in the popliteal vein at 500 U/min (n = 3), or at 100 U/min (n = 3). Saline was administered in the opposite leg. After the animals were killed, the mass of thrombus in the iliofemoral veins was measured. The pudendoepiploic (PEV), profunda femoris (PF), and popliteal veins (PV) were examined. Thrombosis in the tributaries of the superficial femoral vein (SFVt) was graded according to a three-point scale (0, +, ++). In part II of the study IV administration was further investigated in nine pigs using the following three regimens with 1000 U at 25 U/min serving as the control: (1) 1000 U at 100 U/min, (2) 250 U at 25 U/min, (3) 250 U at 6.25 U/min. All animals survived. In part I median thrombus mass in the test limbs was 1.40 g as compared with 0.25 g in the controls (p = 0.01). PEV, PFV and PV were thrombosed in all limbs infused with thrombin. IV infusion was more effective in inducing thrombosis in both the parent veins (mass 1. 32-1.78 g) and SVFt (++ in 4 of 6 legs), as compared with IA infusion (mass 0.0-1.16 g; SFVt ++ in 1 of 3 legs). In part II thrombus mass in axial veins ranged from 1.23 to 2.86 g, and showed no relationship with the dose of thrombin or the rate of infusion. Tributary thrombosis was less extensive with 250 U at 25 U/min than with the other regimens. Slow distal intravenous thrombin infusion in the hind legs of pigs combined with proximal venous occlusion induces thrombosis in the leg veins that closely resembles clinical DVT in distribution.

Analysis of Muscle Bioenergetic Metabolism in Rabbit Leg Lengthening

The effect of lengthening on muscle metabolism was measured and correlated to the percent lengthening at early and late time points. Using the rabbit tibial lengthening model, the authors examined the effects of lengthening on the tibialis anterior muscle using phosphorus-31 magnetic resonance spectroscopy. Thirty-six rabbits were divided into five groups, four groups by percent lengthening (0%, 15%, 20%, and 25%), with each group divided into subgroups of early (end distraction) and late (12 weeks after end distraction), and the fifth group using the opposite untreated leg as control. Several parameters measuring metabolism of muscle using phosphorus-31 magnetic resonance spectroscopy analysis were compared. No changes occurred to 15% lengthening, but significant decreases were measured at 20% and 25% lengthening. After a 25% lengthening, the decreased metabolism persisted at 12 weeks after distraction, indicating the possibility of permanent damage. After 20% lengthening, the same parameters improved but never to normal levels. The authors conclude that lengthening to 15% is safe for muscle, but 20% to 25% lengthening may result in permanent metabolic damage. The current study also suggests that phosphorus-31 magnetic resonance spectroscopy may provide a viable clinical method for evaluating muscle damage during lengthening.

Ipsilateral Island Fibula Transfer for Segmental Tibial Defects: Antegrade and Retrograde Fashion

Five patients with segmental tibial defects whose contralateral fibula could not be used as a donor were treated with ipsilateral island fibular transfer in an antegrade or retrograde fashion. Antegrade-flow pedicled flaps based on the peroneal vessel as in the conventional free flap were used for the proximal or middle one-third tibial defects, whereas retrograde-flow pedicled flaps based on the communicating branch between the peroneal and posterior tibial vessels were used for the middle or distal one-third of the tibia. All patients had one of the following problems: a previously failed free flap, below-knee amputation of the opposite leg because of open tibia fracture, refusal to use the contralateral sound leg, or poor general condition to endure a lengthy operation. Four of the patients also had an associated fibular fracture on the same leg, which was ultimately used as one of the osteotomy sites. The follow-up period was from 31 to 48 months. Time to bony union ranged from 4 to 7 months. Time to full weight bearing was from 5 to 9 months after operation. All of the transferred fibulas showed hypertrophy after weight bearing. Nonunion occurred in two cases, which were treated with a long leg cast and cancellous bone graft, respectively. The limb was shorter by an average of 0.5 cm in three cases, longer by 1.1 cm in one case, and in the last case, it was uncheckable because the opposite limb was previously amputated. Limited arc of rotation was not a problem. Other disabling complications were not seen. We believe that these methods can be a valuable alternative to the contralateral free fibula flap in certain cases.

Hyperalgesia and temporal summation of pain after heat injury in man

Temporal summation of pain occurs when repeated stimuli become increasingly painful in spite of unchanged stimulus intensity. Summation can be quantified as the difference in pain between the first and the last stimulus in a train of stimuli. The aim of the study was to compare temporal summation of pain in normal skin with summation of pain in skin with primary and secondary hyperalgesia evoked by a heat injury. A heat injury was produced on the crus of 12 volunteers with a 50×25 mm thermode (47°C, 7 min). Measurements were made before, and 0, 1, 2, and 4 h after the heat injury, in three areas: primary and secondary mechanical hyperalgesia induced by the heat injury, and in a mirror image of the injury on the opposite leg. Temporal summation of pain was induced by repeated electrical stimuli (five stimuli at 2 Hz) and assessed by visual analog scale (VAS). Primary hyperalgesia was evaluated by von Frey hairs and electrical stimuli, and the areas of secondary hyperalgesia with a rigid von Frey hair (314 mN). Significant primary ( P<0.000001) and secondary ( P<0.00006) mechanical hyperalgesia were evoked by the heat injury. The pain threshold to single electrical stimuli was reduced within the injury ( P<0.03), but not outside. The pain responses to single and repeated electrical stimuli were not significantly altered by the injury. Temporal summation of pain occurred in 418 stimulus trains out of 576 (73%), but no significant changes in summation developed in skin with primary or secondary mechanical hyperalgesia compared with normal skin (baseline measurements). Temporal summation at high stimulus intensities was more pronounced than at lower intensities ( P<0.0002). We found no correlation between either temporal summation and area of secondary hyperalgesia, or temporal summation and pain intensity during the induction of heat injury. We conclude that the development of primary and secondary mechanical hyperalgesia after heat injury in man was not associated with changes in temporal summation of painful electrical stimuli.

Sciatic nerve: paradoxic hypertrophy after amputation in young patients.

To evaluate the appearance of the sciatic nerve after leg amputation. Magnetic resonance (MR) images were obtained in seven patients (age at amputation, 11-19 years) who underwent above-knee amputation to treat osteogenic sarcoma. Images were evaluated for sciatic nerve enlargement. Findings were correlated with the time after amputation. All seven patients were found to have a markedly enlarged sciatic nerve in the stump of the amputated leg. The enlargement extended proximally from the point of nerve transection to a level posterior to the femoral neck (8-27 cm) depending on the length of the stump. No evidence of sciatic nerve enlargement was found in the opposite leg or on preoperative MR images that were available in three of the patients. Moreover, in one patient with a sarcoma who underwent a leg-sparing procedure, no sciatic nerve enlargement was seen postoperatively. The thickness of the distal sciatic nerve was related to the time after amputation. Hypertrophy of the sciatic nerve occurred after above-knee amputation in young patients. This finding differed from atrophy of the nerve that has been reported previously in older patients.

Local anesthesia for infrainguinal arterial reconstruction

Perioperative cardiac complications occur in 4% to 6% of patients undergoing infrainguinal revascularization under general, spinal, or epidural anesthesia. The risk may be even greater in patients whose cardiac disease cannot be fully evaluated or treated before urgent limb salvage operations. Prompted by these considerations, we investigated the feasibility and results of using local anesthesia in these high-risk patients. From January 1, 1994, through August 30, 1996, 86 infrainguinal reconstructions were performed under local infiltration anesthesia (0.5% or 1.0% lidocaine). Supplementary intravenous sedation with propofol or other agents was given as needed for patients comfort. Most patients had arterial lines but Swan Ganz catheters were used infrequently. Postoperatively, continuous electrocardiographic monitoring was continued in the intermediate or intensive care units. Patients ranged in age from 37 to 86 years (mean 68 +/- 12); 47% were diabetic, 69% had severe coronary artery disease, and 14% had end-stage renal disease. Operations included 7 femoral-femoral, 21 femoral-popliteal, 16 femoral-tibial and 13 popliteal-tibial bypass grafts, 9 pseudoaneurysms, and 20 distal graft revisions (+/- thrombectomy). Autogenous vein was used in eight of the femoral-popliteal and all of the femoral-tibial and popliteal-tibial bypass grafts. There were two postoperative deaths. One patient died of a stroke (1.2%) on postoperative day (POD) 2 and one died on POD 27 of unknown cause. Two other (2%) patients had nonfatal subendocardial myocardial infarctions. Conversion to general anesthesia was required in four (5%) operations, three because patients became agitated and one because a long segment of vein had to be harvested from the opposite leg. Otherwise, patients tolerated the procedures well and postanesthetic recovery problems were minimized. Limb salvage operations can be done under local anesthesia with acceptable complication rates. In selected patients with high-risk coronary artery disease, local anesthesia has theoretic and practical advantages and should be considered an alternative to general or regional anesthesia.

Quantitative assessment of callus distraction using dual energy X-ray absorptiometry.

Bone mineralisation during and after limb lengthening procedures on the femur or tibia using unilateral fixators has been monitored quantitatively using dual energy X-ray absorptiometry (DEXA). We measured the bone mineral density (BMD) prospectively in the newly formed callus, in the bone adjacent to the callus and in the proximal femur. In twenty-one patients we showed a typical course with a peak value at 4-6 weeks after beginning distraction and a minimum value at maximum distraction. In the consolidation period the BMD in the distraction gap increased until the fixator was removed. The BMD in the regenerated bone increased faster in the regions of interest (ROI) opposite the fixator compared to those near it. Dynamisation caused more homogeneous regeneration equalising VBMD in the different ROIs. The BMD in the proximal femur of the leg which was operated on decreased to 67% and in the opposite leg to 87% of the preoperative value. DEXA provides a precise and quantitative assessment of callus and bone mineralisation during limb lengthening and helps in understanding what is happening during these procedures.